X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=5a65422cb009b42360c0ef2c5b83134ad7c75b01;hp=f06b1283d418a529e8196150a5de85e8b934bd02;hb=b9f5d1c6ff1193d7409065322a76f59385baee3e;hpb=e4277c06bfb783b5ec78001eeef06fa9feae033f diff --git a/src/pawns.cpp b/src/pawns.cpp index f06b1283..5a65422c 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -1,7 +1,7 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2009 Marco Costalba + Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -17,389 +17,265 @@ along with this program. If not, see . */ - -//// -//// Includes -//// - +#include #include -#include +#include "bitboard.h" #include "bitcount.h" #include "pawns.h" #include "position.h" - -//// -//// Local definitions -//// - namespace { - /// Constants and variables - - // Doubled pawn penalty by file, middle game - const Value DoubledPawnMidgamePenalty[8] = { - Value(13), Value(20), Value(23), Value(23), - Value(23), Value(23), Value(20), Value(13) + #define V Value + #define S(mg, eg) make_score(mg, eg) + + // Doubled pawn penalty by opposed flag and file + const Score Doubled[2][FILE_NB] = { + { S(13, 43), S(20, 48), S(23, 48), S(23, 48), + S(23, 48), S(23, 48), S(20, 48), S(13, 43) }, + { S(13, 43), S(20, 48), S(23, 48), S(23, 48), + S(23, 48), S(23, 48), S(20, 48), S(13, 43) }}; + + // Isolated pawn penalty by opposed flag and file + const Score Isolated[2][FILE_NB] = { + { S(37, 45), S(54, 52), S(60, 52), S(60, 52), + S(60, 52), S(60, 52), S(54, 52), S(37, 45) }, + { S(25, 30), S(36, 35), S(40, 35), S(40, 35), + S(40, 35), S(40, 35), S(36, 35), S(25, 30) }}; + + // Backward pawn penalty by opposed flag and file + const Score Backward[2][FILE_NB] = { + { S(30, 42), S(43, 46), S(49, 46), S(49, 46), + S(49, 46), S(49, 46), S(43, 46), S(30, 42) }, + { S(20, 28), S(29, 31), S(33, 31), S(33, 31), + S(33, 31), S(33, 31), S(29, 31), S(20, 28) }}; + + // Pawn chain membership bonus by file + const Score ChainMember[FILE_NB] = { + S(11,-1), S(13,-1), S(13,-1), S(14,-1), + S(14,-1), S(13,-1), S(13,-1), S(11,-1) }; - // Doubled pawn penalty by file, endgame - const Value DoubledPawnEndgamePenalty[8] = { - Value(43), Value(48), Value(48), Value(48), - Value(48), Value(48), Value(48), Value(43) + // Candidate passed pawn bonus by rank + const Score CandidatePassed[RANK_NB] = { + S( 0, 0), S( 6, 13), S(6,13), S(14,29), + S(34,68), S(83,166), S(0, 0), S( 0, 0) }; - // Isolated pawn penalty by file, middle game - const Value IsolatedPawnMidgamePenalty[8] = { - Value(25), Value(36), Value(40), Value(40), - Value(40), Value(40), Value(36), Value(25) - }; - - // Isolated pawn penalty by file, endgame - const Value IsolatedPawnEndgamePenalty[8] = { - Value(30), Value(35), Value(35), Value(35), - Value(35), Value(35), Value(35), Value(30) - }; + // Weakness of our pawn shelter in front of the king indexed by [rank] + const Value ShelterWeakness[RANK_NB] = + { V(100), V(0), V(27), V(73), V(92), V(101), V(101) }; + + // Danger of enemy pawns moving toward our king indexed by + // [no friendly pawn | pawn unblocked | pawn blocked][rank of enemy pawn] + const Value StormDanger[3][RANK_NB] = { + { V( 0), V(64), V(128), V(51), V(26) }, + { V(26), V(32), V( 96), V(38), V(20) }, + { V( 0), V( 0), V( 64), V(25), V(13) }}; + + // Max bonus for king safety. Corresponds to start position with all the pawns + // in front of the king and no enemy pawn on the horizont. + const Value MaxSafetyBonus = V(263); + + #undef S + #undef V + + template + Score evaluate(const Position& pos, Pawns::Entry* e) { + + const Color Them = (Us == WHITE ? BLACK : WHITE); + const Square Up = (Us == WHITE ? DELTA_N : DELTA_S); + const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW); + const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE); + + Bitboard b; + Square s; + File f; + Rank r; + bool passed, isolated, doubled, opposed, chain, backward, candidate; + Score value = SCORE_ZERO; + const Square* pl = pos.list(Us); + + Bitboard ourPawns = pos.pieces(Us, PAWN); + Bitboard theirPawns = pos.pieces(Them, PAWN); + + e->passedPawns[Us] = 0; + e->kingSquares[Us] = SQ_NONE; + e->semiopenFiles[Us] = 0xFF; + e->pawnAttacks[Us] = shift_bb(ourPawns) | shift_bb(ourPawns); + e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares); + e->pawnsOnSquares[Us][WHITE] = pos.count(Us) - e->pawnsOnSquares[Us][BLACK]; - // Backward pawn penalty by file, middle game - const Value BackwardPawnMidgamePenalty[8] = { - Value(20), Value(29), Value(33), Value(33), - Value(33), Value(33), Value(29), Value(20) - }; + // Loop through all pawns of the current color and score each pawn + while ((s = *pl++) != SQ_NONE) + { + assert(pos.piece_on(s) == make_piece(Us, PAWN)); + + f = file_of(s); + r = rank_of(s); + + // This file cannot be semi-open + e->semiopenFiles[Us] &= ~(1 << f); + + // Our rank plus previous one. Used for chain detection + b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1)); + + // Flag the pawn as passed, isolated, doubled or member of a pawn + // chain (but not the backward one). + chain = ourPawns & adjacent_files_bb(f) & b; + isolated = !(ourPawns & adjacent_files_bb(f)); + doubled = ourPawns & forward_bb(Us, s); + opposed = theirPawns & forward_bb(Us, s); + passed = !(theirPawns & passed_pawn_mask(Us, s)); + + // Test for backward pawn. + // If the pawn is passed, isolated, or member of a pawn chain it cannot + // be backward. If there are friendly pawns behind on adjacent files + // or if can capture an enemy pawn it cannot be backward either. + if ( (passed | isolated | chain) + || (ourPawns & pawn_attack_span(Them, s)) + || (pos.attacks_from(s, Us) & theirPawns)) + backward = false; + else + { + // We now know that there are no friendly pawns beside or behind this + // pawn on adjacent files. We now check whether the pawn is + // backward by looking in the forward direction on the adjacent + // files, and seeing whether we meet a friendly or an enemy pawn first. + b = pos.attacks_from(s, Us); - // Backward pawn penalty by file, endgame - const Value BackwardPawnEndgamePenalty[8] = { - Value(28), Value(31), Value(31), Value(31), - Value(31), Value(31), Value(31), Value(28) - }; + // Note that we are sure to find something because pawn is not passed + // nor isolated, so loop is potentially infinite, but it isn't. + while (!(b & (ourPawns | theirPawns))) + b = shift_bb(b); - // Pawn chain membership bonus by file, middle game - const Value ChainMidgameBonus[8] = { - Value(11), Value(13), Value(13), Value(14), - Value(14), Value(13), Value(13), Value(11) - }; + // The friendly pawn needs to be at least two ranks closer than the + // enemy pawn in order to help the potentially backward pawn advance. + backward = (b | shift_bb(b)) & theirPawns; + } - // Pawn chain membership bonus by file, endgame - const Value ChainEndgameBonus[8] = { - Value(-1), Value(-1), Value(-1), Value(-1), - Value(-1), Value(-1), Value(-1), Value(-1) - }; + assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns)); - // Candidate passed pawn bonus by rank, middle game - const Value CandidateMidgameBonus[8] = { - Value( 0), Value( 6), Value(6), Value(14), - Value(34), Value(83), Value(0), Value( 0) - }; + // A not passed pawn is a candidate to become passed if it is free to + // advance and if the number of friendly pawns beside or behind this + // pawn on adjacent files is higher or equal than the number of + // enemy pawns in the forward direction on the adjacent files. + candidate = !(opposed | passed | backward | isolated) + && (b = pawn_attack_span(Them, s + pawn_push(Us)) & ourPawns) != 0 + && popcount(b) >= popcount(pawn_attack_span(Us, s) & theirPawns); - // Candidate passed pawn bonus by rank, endgame - const Value CandidateEndgameBonus[8] = { - Value( 0), Value( 13), Value(13), Value(29), - Value(68), Value(166), Value( 0), Value( 0) - }; + // Passed pawns will be properly scored in evaluation because we need + // full attack info to evaluate passed pawns. Only the frontmost passed + // pawn on each file is considered a true passed pawn. + if (passed && !doubled) + e->passedPawns[Us] |= s; - // Pawn storm tables for positions with opposite castling - const int QStormTable[64] = { - 0, 0, 0, 0, 0, 0, 0, 0, - -22,-22,-22,-14,-6, 0, 0, 0, - -6,-10,-10,-10,-6, 0, 0, 0, - 4, 12, 16, 12, 4, 0, 0, 0, - 16, 23, 23, 16, 0, 0, 0, 0, - 23, 31, 31, 23, 0, 0, 0, 0, - 23, 31, 31, 23, 0, 0, 0, 0, - 0, 0, 0, 0, 0, 0, 0, 0 - }; + // Score this pawn + if (isolated) + value -= Isolated[opposed][f]; - const int KStormTable[64] = { - 0, 0, 0, 0, 0, 0, 0, 0, - 0, 0, 0,-10,-19,-28,-33,-33, - 0, 0, 0,-10,-15,-19,-24,-24, - 0, 0, 0, 0, 1, 1, 1, 1, - 0, 0, 0, 0, 1, 10, 19, 19, - 0, 0, 0, 0, 1, 19, 31, 27, - 0, 0, 0, 0, 0, 22, 31, 22, - 0, 0, 0, 0, 0, 0, 0, 0 - }; + if (doubled) + value -= Doubled[opposed][f]; - // Pawn storm open file bonuses by file - const int16_t KStormOpenFileBonus[8] = { 31, 31, 18, 0, 0, 0, 0, 0 }; - const int16_t QStormOpenFileBonus[8] = { 0, 0, 0, 0, 0, 26, 42, 26 }; + if (backward) + value -= Backward[opposed][f]; - // Pawn storm lever bonuses by file - const int StormLeverBonus[8] = { -8, -8, -13, 0, 0, -13, -8, -8 }; + if (chain) + value += ChainMember[f]; -} + if (candidate) + value += CandidatePassed[relative_rank(Us, s)]; + } + return value; + } -//// -//// Functions -//// +} // namespace -/// Constructor +namespace Pawns { -PawnInfoTable::PawnInfoTable(unsigned numOfEntries) { +/// probe() takes a position object as input, computes a Entry object, and returns +/// a pointer to it. The result is also stored in a hash table, so we don't have +/// to recompute everything when the same pawn structure occurs again. - size = numOfEntries; - entries = new PawnInfo[size]; - if (!entries) - { - std::cerr << "Failed to allocate " << (numOfEntries * sizeof(PawnInfo)) - << " bytes for pawn hash table." << std::endl; - Application::exit_with_failure(); - } -} +Entry* probe(const Position& pos, Table& entries) { + Key key = pos.pawn_key(); + Entry* e = entries[key]; -/// Destructor + if (e->key == key) + return e; -PawnInfoTable::~PawnInfoTable() { - delete [] entries; + e->key = key; + e->value = evaluate(pos, e) - evaluate(pos, e); + return e; } -/// PawnInfo::clear() resets to zero the PawnInfo entry. Note that -/// kingSquares[] is initialized to SQ_NONE instead. - -void PawnInfo::clear() { +/// Entry::shelter_storm() calculates shelter and storm penalties for the file +/// the king is on, as well as the two adjacent files. - memset(this, 0, sizeof(PawnInfo)); - kingSquares[WHITE] = kingSquares[BLACK] = SQ_NONE; -} +template +Value Entry::shelter_storm(const Position& pos, Square ksq) { + const Color Them = (Us == WHITE ? BLACK : WHITE); -/// PawnInfoTable::get_pawn_info() takes a position object as input, computes -/// a PawnInfo object, and returns a pointer to it. The result is also -/// stored in a hash table, so we don't have to recompute everything when -/// the same pawn structure occurs again. + Value safety = MaxSafetyBonus; + Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq)); + Bitboard ourPawns = b & pos.pieces(Us); + Bitboard theirPawns = b & pos.pieces(Them); + Rank rkUs, rkThem; + File kf = file_of(ksq); -PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) { + kf = (kf == FILE_A) ? FILE_B : (kf == FILE_H) ? FILE_G : kf; - assert(pos.is_ok()); + for (int f = kf - 1; f <= kf + 1; f++) + { + b = ourPawns & FileBB[f]; + rkUs = b ? relative_rank(Us, Us == WHITE ? lsb(b) : msb(b)) : RANK_1; + safety -= ShelterWeakness[rkUs]; - Key key = pos.get_pawn_key(); - int index = int(key & (size - 1)); - PawnInfo* pi = entries + index; + b = theirPawns & FileBB[f]; + rkThem = b ? relative_rank(Us, Us == WHITE ? lsb(b) : msb(b)) : RANK_1; + safety -= StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem]; + } - // If pi->key matches the position's pawn hash key, it means that we - // have analysed this pawn structure before, and we can simply return - // the information we found the last time instead of recomputing it. - if (pi->key == key) - return pi; + return safety; +} - // Clear the PawnInfo object, and set the key - pi->clear(); - pi->key = key; - Value mgValue[2] = {Value(0), Value(0)}; - Value egValue[2] = {Value(0), Value(0)}; +/// Entry::update_safety() calculates and caches a bonus for king safety. It is +/// called only when king square changes, about 20% of total king_safety() calls. - // Loop through the pawns for both colors - for (Color us = WHITE; us <= BLACK; us++) - { - Color them = opposite_color(us); - Bitboard ourPawns = pos.pieces(PAWN, us); - Bitboard theirPawns = pos.pieces(PAWN, them); - Bitboard pawns = ourPawns; - - // Initialize pawn storm scores by giving bonuses for open files - for (File f = FILE_A; f <= FILE_H; f++) - if (!(pawns & file_bb(f))) - { - pi->ksStormValue[us] += KStormOpenFileBonus[f]; - pi->qsStormValue[us] += QStormOpenFileBonus[f]; - pi->halfOpenFiles[us] |= (1 << f); - } +template +Score Entry::update_safety(const Position& pos, Square ksq) { - // Loop through all pawns of the current color and score each pawn - while (pawns) - { - Square s = pop_1st_bit(&pawns); - File f = square_file(s); - Rank r = square_rank(s); - - assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN)); - - // Passed, isolated or doubled pawn? - bool passed = Position::pawn_is_passed(theirPawns, us, s); - bool isolated = Position::pawn_is_isolated(ourPawns, s); - bool doubled = Position::pawn_is_doubled(ourPawns, us, s); - - // We calculate kingside and queenside pawn storm - // scores for both colors. These are used when evaluating - // middle game positions with opposite side castling. - // - // Each pawn is given a base score given by a piece square table - // (KStormTable[] or QStormTable[]). Pawns which seem to have good - // chances of creating an open file by exchanging itself against an - // enemy pawn on an adjacent file gets an additional bonus. - - // Kingside pawn storms - int bonus = KStormTable[relative_square(us, s)]; - if (f >= FILE_F) - { - Bitboard b = outpost_mask(us, s) & theirPawns & (FileFBB | FileGBB | FileHBB); - while (b) - { - Square s2 = pop_1st_bit(&b); - if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2))) - { - // The enemy pawn has no pawn beside itself, which makes it - // particularly vulnerable. Big bonus, especially against a - // weakness on the rook file. - if (square_file(s2) == FILE_H) - bonus += 4*StormLeverBonus[f] - 8*square_distance(s, s2); - else - bonus += 2*StormLeverBonus[f] - 4*square_distance(s, s2); - } else - // There is at least one enemy pawn beside the enemy pawn we look - // at, which means that the pawn has somewhat better chances of - // defending itself by advancing. Smaller bonus. - bonus += StormLeverBonus[f] - 2*square_distance(s, s2); - } - } - pi->ksStormValue[us] += bonus; + kingSquares[Us] = ksq; + castleRights[Us] = pos.can_castle(Us); + minKPdistance[Us] = 0; - // Queenside pawn storms - bonus = QStormTable[relative_square(us, s)]; - if (f <= FILE_C) - { - Bitboard b = outpost_mask(us, s) & theirPawns & (FileABB | FileBBB | FileCBB); - while (b) - { - Square s2 = pop_1st_bit(&b); - if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2))) - { - // The enemy pawn has no pawn beside itself, which makes it - // particularly vulnerable. Big bonus, especially against a - // weakness on the rook file. - if (square_file(s2) == FILE_A) - bonus += 4*StormLeverBonus[f] - 16*square_distance(s, s2); - else - bonus += 2*StormLeverBonus[f] - 8*square_distance(s, s2); - } else - // There is at least one enemy pawn beside the enemy pawn we look - // at, which means that the pawn has somewhat better chances of - // defending itself by advancing. Smaller bonus. - bonus += StormLeverBonus[f] - 4*square_distance(s, s2); - } - } - pi->qsStormValue[us] += bonus; - - // Member of a pawn chain (but not the backward one)? We could speed up - // the test a little by introducing an array of masks indexed by color - // and square for doing the test, but because everything is hashed, - // it probably won't make any noticable difference. - bool chain = ourPawns - & neighboring_files_bb(f) - & (rank_bb(r) | rank_bb(r - (us == WHITE ? 1 : -1))); - - // Test for backward pawn - // - // If the pawn is passed, isolated, or member of a pawn chain - // it cannot be backward. If can capture an enemy pawn or if - // there are friendly pawns behind on neighboring files it cannot - // be backward either. - bool backward; - if ( passed - || isolated - || chain - || (pos.attacks_from(s, us) & theirPawns) - || (ourPawns & behind_bb(us, r) & neighboring_files_bb(f))) - backward = false; - else - { - // We now know that there are no friendly pawns beside or behind this - // pawn on neighboring files. We now check whether the pawn is - // backward by looking in the forward direction on the neighboring - // files, and seeing whether we meet a friendly or an enemy pawn first. - Bitboard b = pos.attacks_from(s, us); - if (us == WHITE) - { - for ( ; !(b & (ourPawns | theirPawns)); b <<= 8); - backward = (b | (b << 8)) & theirPawns; - } - else - { - for ( ; !(b & (ourPawns | theirPawns)); b >>= 8); - backward = (b | (b >> 8)) & theirPawns; - } - } + Bitboard pawns = pos.pieces(Us, PAWN); + if (pawns) + while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {} - // Test for candidate passed pawn - bool candidate; - candidate = !passed - && !(theirPawns & file_bb(f)) - && ( count_1s_max_15(neighboring_files_bb(f) & (behind_bb(us, r) | rank_bb(r)) & ourPawns) - - count_1s_max_15(neighboring_files_bb(f) & in_front_bb(us, r) & theirPawns) - >= 0); + if (relative_rank(Us, ksq) > RANK_4) + return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]); - // In order to prevent doubled passed pawns from receiving a too big - // bonus, only the frontmost passed pawn on each file is considered as - // a true passed pawn. - if (passed && (ourPawns & squares_in_front_of(us, s))) - passed = false; + Value bonus = shelter_storm(pos, ksq); - // Score this pawn - if (passed) - set_bit(&(pi->passedPawns), s); + // If we can castle use the bonus after the castle if is bigger + if (pos.can_castle(make_castle_right(Us, KING_SIDE))) + bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_G1))); - if (isolated) - { - mgValue[us] -= IsolatedPawnMidgamePenalty[f]; - egValue[us] -= IsolatedPawnEndgamePenalty[f]; - if (!(theirPawns & file_bb(f))) - { - mgValue[us] -= IsolatedPawnMidgamePenalty[f] / 2; - egValue[us] -= IsolatedPawnEndgamePenalty[f] / 2; - } - } - if (doubled) - { - mgValue[us] -= DoubledPawnMidgamePenalty[f]; - egValue[us] -= DoubledPawnEndgamePenalty[f]; - } - if (backward) - { - mgValue[us] -= BackwardPawnMidgamePenalty[f]; - egValue[us] -= BackwardPawnEndgamePenalty[f]; - if (!(theirPawns & file_bb(f))) - { - mgValue[us] -= BackwardPawnMidgamePenalty[f] / 2; - egValue[us] -= BackwardPawnEndgamePenalty[f] / 2; - } - } - if (chain) - { - mgValue[us] += ChainMidgameBonus[f]; - egValue[us] += ChainEndgameBonus[f]; - } - if (candidate) - { - mgValue[us] += CandidateMidgameBonus[relative_rank(us, s)]; - egValue[us] += CandidateEndgameBonus[relative_rank(us, s)]; - } - } // while(pawns) - } // for(colors) + if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE))) + bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); - pi->mgValue = int16_t(mgValue[WHITE] - mgValue[BLACK]); - pi->egValue = int16_t(egValue[WHITE] - egValue[BLACK]); - return pi; + return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]); } +// Explicit template instantiation +template Score Entry::update_safety(const Position& pos, Square ksq); +template Score Entry::update_safety(const Position& pos, Square ksq); -/// PawnInfo::updateShelter calculates and caches king shelter. It is called -/// only when king square changes, about 20% of total get_king_shelter() calls. -int PawnInfo::updateShelter(const Position& pos, Color c, Square ksq) { - - unsigned shelter = 0; - Bitboard pawns = pos.pieces(PAWN, c) & this_and_neighboring_files_bb(ksq); - unsigned r = ksq & (7 << 3); - for (int i = 1, k = (c ? -8 : 8); i < 4; i++) - { - r += k; - shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (128 >> i); - } - kingSquares[c] = ksq; - kingShelters[c] = shelter; - return shelter; -} +} // namespace Pawns